This invention relates to detergent compositions containing peroxybleach activators. In particular, this invention pertains to detergent compositions comprising particulate crystalline peroxybleach activators having a coarse particle diameter and a well-defined rate of hydrolysis. The particulate peroxybleach activator can also be represented by an agglomerate of a peroxybleach activator and a chemically inert, versus the activator, agglomerating agent having a melting point in the range from about 25.degree. C to about 100.degree. C. Detergent compositions containing the particulate bleach activator, either crystalline or as an agglomerate, of this invention retain their original performance and appearance characteristics after a prolonged storage. The use of oxygen bleach components in detergent formulae is well known and had found widespread commercial acceptance. During the laundering operation, peroxybleach components release the active oxygen at temperatures in the range from about 60.degree. C up to the boil. The active oxygen provides bleaching and cleaning enhancement through chemical interaction with the soil, for example, through oxidation and hydrolytic cleavage. In up to the boil perbleach laundering operations, not all the active oxygen of the peroxybleach component will be released for cleaning and bleaching purposes. In addition, oxygen bleach-containing detergent compositions for up to the boil laundering operations cannot be used effectively in many laundering machines used by housewives.
The above disadvantages are well known and much effort has been spent to provide laundering compositions capable of releasing the active oxygen at a temperature in the range from, for example, ambient temperature to about 60.degree. C. This can be achieved through the incorporation of a peroxybleach activator which is capable of facilitating the active oxygen release at lower temperatures, for example, in the range from about ambient temperature to about 60.degree. C. Concurrently, the activator catalyzes the active oxygen release to obtain a more quantitative use of the peroxybleach component in the detergent composition.
It is well known that peroxybleach activator-containing detergent compositions suffer from activator instability and component-incompatibility due to the chemical affinity of the activator to sensitive co-ingredients, particularly during prolonged storage. These shortcomings apparently relate to the chemical reactivity of the activator, to wit, hydrolysis and perhydrolysis. The activator in conjunction with formula moisture forms undesirable hydrolysis and perhydrolysis products during storage. These (hydrolysis and perhydrolysis) reaction products are, of course, not available for laundering purposes. These products of hydrolysis and perhydrolysis can also react with the more sensitive ingredients in the detergent formulae to thereby render them less effective in achieving their function. Examples of the like components include perfumes, optical brighteners, enzymatic ingredients, dyes, etc. The incompatibility of the optical brightener (or its impurities) in presence of a peroxybleach activator can be a problem in formulating detergent compositions. This can result in the formation of a distinct and undesirable pink or yellow hue in the finished product.
The peroxybleach activator materials currently available being deficient for the reasons set out hereinbefore, there is a standing desire to formulate low-temperature bleach detergent compositions which provide the expected advantages of low-temperature bleach compositions, but at the same time do not possess the shortcomings which render them less attractive for commercialization.
It is a main object of this invention to provide an activated bleach detergent composition having an improved stability and a superior performance after a prolonged storage.
It is an additional object of this invention to provide an activated bleach detergent composition the appearance of which will remain substantially unchanged (storage stable) even in the presence of an optical brightener.
The above and other advantages, as is apparent from the following description, can be provided by the invention disclosed hereinafter.
It has now been discovered that granular activated peroxybleach containing detergent compositions can be prepared having desirable storage stability, appearance and performance properties.
In more detail, this invention broadly encompasses the addition of a particulate perbleach activator, having a narrow particle diameter and a specific rate of hydrolysis to a peroxybleach detergent composition. The activator either can meet the definition of this invention as a uniform and coarse crystalline activator component or as an agglomerate of a finely divided activator and a suitable agglomerating agent. The peroxybleach activator is further characterized by a rate of hydrolysis in the range from about 45% to 5% by weight under the testing conditions set forth in the following.
The essential and some additional components of this invention are described in more details hereinafter.
Unless indicated to the contrary in the following description of the invention the "%" indications stand for percent by weight.
The perbleach activator component herein can be represented by a crystalline species having a mean particle diameter in the range from about 1.8 mm to about 0.5 mm, preferably from 1.6 mm to about 1.0 mm. An average particle diameter of more than about 1.8 mm has been found to be less suitable for use in detergent compositions because of an increased tendency to segregate and also because the dissolving speed can diminish to the point where it could not anymore provide all the advantages of this invention within the time limit of the laundering operation. The lower particle diameter appears to be critical inasmuch as a crystalline activator component having a mean particle distribution of less than 0.5 mm is prone to a markedly decreased storage stability which, of course, can adversely affect the appearance and performance characteristics of, for example, the detergent composition into which the activator, either crystalline or as an agglomerate, is incorporated.
The average particle diameter can be selected and determined with the aid of the usual means incluse of sieves (any calibrated series), microscopic determinations and so on.
The activator component is furthermore defined by its loss of activity which can be measured with the following analytical technique.